1. Field of the Invention
The present invention relates to the area of blood vessel graft systems in general. More particularly, this invention provides a catheter base deployment system for multi-layered stent grafts comprising multiple coaxial delivery mechanisms. By using the coaxial delivery mechanism system, the multiple layers of the stent graft can be assembled endovascularly.
2. Description of Related Art
Aortic aneurysms are a common type of deteriorating disease caused by weakening of the wall of a blood vessel. The weakened wall, under the pressure of flowing blood, balloons outward. Such a deformity in the wall of a blood vessel not only affects its ability to conduct blood, but also is potentially fatal if a rupture occurs at the site of the aneurysm.
Traditionally, the treatment for aneurysms entailed removing part or all of the aneurysm and implanting a replacement prosthetic section into the lumen. Alternatively, a synthetic or biomaterial graft is sutured end-to-end completely replacing the excised portion of the blood vessel. However, surgical treatment or removal of the aneurysm involves significant invasive techniques, extended hospitalization and associated risk of complications. Complications include extensive blood loss, respiratory tract infections, wound infections, and renal failure. In addition, the mortality rates (8%) are significant for such surgeries.
A more contemporary method of treatment of aneurysms is to place a graft within the lumen of the weakened blood vessel via a catheter-based device. Conventional tubular aortic replacement sections, however, are generally larger in diameter than the femoral artery, and therefore cannot be inserted through the lumen of the femoral artery. The basic concept of a transluminal placement of an endovascular prosthesis for decreasing risk associated with the surgical repair of aortic aneurysms was first experimentally investigated by Balko (J. Surg Res 1986; 40:305-09). Since then, several investigators have studied the feasibility of different endovascular devices. For example Lazarus (U.S. Pat. No. 5,669,936) discloses a graft system having a capsule catheter that is deployed after femoral arteriotomy. To date, stent-grafts used clinically for treatment of abdominal and thoracic aortic aneurysms have required large, 18-F to 30-F delivery systems. The large size of the delivery system necessitated surgical femoral artenotomy, and sometimes retroperitoneal left iliac arteriotomy or distal aorta aortotomy, igeneral anesthesia, and high levels of multidisciplinary cooperation. Occasionally, relatively healthy iliac vessels with large diameters are needed in patients with highly sclerotic tortuous iliac arteries; angioplasty with or without stenting was necessary for performance of endovascular grafting. None of the clinically used devices is suitable for percutaneous insertion; all require a femoral arteriotomy because of their size.
Recently, a catheter-based system for the delivery of grafts for repair of aortic aneurysms was disclosed by Taheri et al. (U.S. Pat. No. 5,713,917 and U.S. Pat. No. 5,591,195). The system includes a single stage graft comprised of two nitinol springs. The two nitinol springs are in physical communication with each other via a nitinol connecting bar and are embedded in graft material at each end and covered completely by material so as to prevent direct exposure to bodily fluids or tissues. The graft is deployed by using an elongated sheath introducer having an axially extending sheath passage for receiving the graft and maintaining it in a compressed condition. A flexible push rod around the insertion catheter and within the sheath passage is used to push the graft out of the sheath during deployment.
In theory, one way to decrease the size of an endovascular device is to deploy the stent graft as separate parts. However, none of the delivery devices available are suitable for delivery of a multi-stage stent graft by a single percutaneous insertion. There is thus ongoing need for graft delivery devices for treatment of aneurysms which require minimal preparation and hospitalization.